Iterating over strings in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does it mean to iterate over a string in Python?

Iterating over a string means going through each character one by one, like reading a word letter by letter.

beginner

How do you write a simple loop to print each character of the string "hello"?

Use a for loop like this:<br>

for char in "hello":
    print(char)

beginner

Can you change characters of a string by iterating over it?

No, strings are like frozen words. You can read each letter, but you cannot change them directly because strings are immutable.

beginner

What will this code print?<br>

for c in "abc":
    print(c.upper())

It prints:<br>

A
B
C

<br>Each letter is converted to uppercase before printing.

intermediate

How can you get the index of each character while iterating over a string?

Use the enumerate() function:<br>

for index, char in enumerate("hello"):
    print(index, char)

What does the following code do?<br>

for ch in "cat":
    print(ch)

A Prints each letter of the word 'cat' on a new line

B Prints the whole word 'cat' three times

C Prints the word 'cat' once

D Causes an error

The loop goes through each character and prints it, so each letter appears on its own line.

Which statement is true about strings in Python?

A You can change characters in a string by assigning new values

B Strings are lists of characters that can be modified

C Strings are immutable, so you cannot change characters directly

D Strings cannot be iterated over

Strings cannot be changed after creation; they are immutable.

How do you get both the index and character when looping over a string?

A Use the split() method

B Use a normal for loop with range and indexing

C Use the len() function only

D Use the enumerate() function

The enumerate() function gives both index and character during iteration.

What will this code print?<br>

for c in "dog":
    print(c.upper())

A D<br>O<br>G

B dog

C DOG

D d<br>o<br>g

Each character is printed in uppercase on its own line.

Which of these is NOT a way to iterate over a string?

A Using a while loop with an index

B Using the string's reverse() method

C Using enumerate() in a for loop

D Using a for loop directly on the string

Strings do not have a reverse() method; you can reverse with slicing but not by reverse() method.

Explain how to loop through each character in a string and print it.

Think about reading a word letter by letter.

Describe why you cannot change characters in a string while iterating over it.

Strings are like frozen words.